P.ROCE$$ OPTIMI$ATION $A� NG$*

i1clor J. Tume/1, P.E., Process/EnVI(onmencal Engmeer, Penta Engmeering Corp., USA, explores methods of increasing the value of capital mvesrmenrs by optimising manufacturing processes, mcreasing production and reducing operarmg costs.

QT\l! II'ANISH TAANSLAHON. PU� RffER TOTHl Sl't:CIAl SECnON AT THE BACK Of THE ISSUE

Introduction Cement plant owners, managers and te

Figure I. In this example, the kiln exit gas flow rate was held at a constant level and the fuel firing rate, clinker production and clinker cooler efficiency were allowed to vary.

Kiln operators at a number of plants vosoted main· taon shallower clinker bed depths than could be achoevable Wlth the existing undergratc fans. By oncreasing and optimising clinker bed depth, koln operators can increase combustion aor temperature and hence, clonker cooler efficiency. In some cases, it may be c

-

Operattonal changes resulttng from drueastng luln ftnng hood leakage from 10� of the total air entenng the ktln to 2% on a preheater kiln system wi th a grate cooler are shown in Table 2.

1- 2. R....,tts of cH

ing items may significantly improve heat transfer efficiency in the kiln system:

• Refractory system in the kiln, pre· heater and cooler.

• The chain system of kilns equipped with a chain system.

• Preheater vessel thimbles. • Preheater meal distribution boxes dis

charging materials from one preheater vessel to other.

• Airlocks at the preheater vessels' discharge.

• Preheater cyclones including inlets and other areas.

�

r • 2 � .,

a m � " .!i

1(; 12 ij 4 0

... "li

·12 -16

0

8

Alternative fuels Table 5. l'olmtial �vlngs of reduong kan exit gM � �>«•tentage to.-In all the examples illust rated above, the objective was to reduce specific fuel con· sumption and oncrease clinker production. Thos example presents alternatove fuels that may be fully or partially substituted for existing fuels to reduce fuel costs. Fuels used in some cement plants as either the main fuel or as a supplement onclude natural gas, fuel oils, coal, petroleum coke, tyres, domestic refuse, rice husks, wood chips and a wide range of waste sol· vents and other organic liquids.

pro

Numerous older technology packing machines. which use mechanical weights on a balance, are cur· rently in operation. In some cases, these packong mach1nes cause bag weoghts to vary by as much as 3%. Therefore, to ensure the minimum weight In each bag, the plant will typically put an additional 2 3% of cement on each bag

In recent years, improvements made to packong machones have yielded machines with significantly more control of the weight of each bag. Weight tol· erances in the range of 0.5% are now achoevable.

These weoght tolerances are achreved by the fol lowong:

• Placing a weighing devoce after the bag packtr that feeds back the weight of each bag to the packing machine.

• Installing a bag filling system that constantly adjusts the amount of cement based on the feed back obta1ned from the wcoghing devKe

• Installing hardware and software to accomplish th� control descrobed above.

Some plants may obtaon significant savongs by reduc ing the weight varoation from bag to bag For exam· pie, on a plant selling 500 000 tpa of cement 1n bags at a production cost of USS4011. a 1% reduction of ctlment per bag could potentially save the plant approximately USS 200 000/yr.

Conclusion This article has presented a number of examples of potential savings achievable by operational changft and small capital onvestmcnts, includrng OPtimlsmg clinker cooler operation, reducing air lnfoltration. optr mising heat transfer, optimising combustion condr· tions, using alternate fuels and t6ntrolling cement bag we1ght variations These potential savings provide an order of magnotude saving, which may vary accordrng to existing plant operating conditions and product ron.

It is important to stress that these are only a sele Ch n -' f"9"'«" 110.-. S.•th

Edttlon. Tobie l· t81 l. GONZALEZ. ,,.. �, 'TM SOuth Ar.,..ocan C.mtnt Industry: M

0vef'Vtew', Pr�'Jenttd .ar r� Jlth IEEE C�nt lnduJUy T�tvwM C0t1fttt·�

Enquiry no: 12

WORLD CEMENT M